VLADKIKAVKAZ, Russia (May 29) - A bomb exploded under the rails as a passenger train traveled by in southern Russia early Saturday, derailing seven cars and slightly injuring about six people, officials said.

Authorities responding to the scene also found a land mine about 150 feet away, but they detonated it without any casualties, police said.

The explosion occurred near the village of Elkhotovo as the train traveled from Moscow to Vladikavkaz, the capital of the province of North Ossetia near Chechnya, regional police spokesman Alan Doyev said, citing preliminary information.

He said the bomb detonated between the third and fourth cars in the 18-car train, which was carrying about 350 people. The force from the 11 pounds of TNT derailed seven cars, he said.

Also Saturday, police opened fire on a suspect on a main street in the Chechen capital of Grozny, killing him and two young bystanders, witnesses said. Two other bystanders were hospitalized with gunshot wounds.

Authorities blocked off the area and refused to comment.

A witness who only gave her first name, Liza, said an unidentified man was fleeing when police opened fire on him. The man and two bystanders, including a young female student, were killed, witnesses said.

Liza told The Associated Press that she was photographing Grozny when the shooting broke out. She said she photographed the incident, but a soldier seized her camera.

An Interior Ministry official, who asked not to be identified, said six people were injured in the train blast. Sergei Kozhemyaka of the southern region's Emergency Situations Ministry, said the injuries were all minor and suffered by people who fell from top bunks in the sleeping carriages.

Russian news agencies reported that the explosive device might have been detonated by remote control because two trains safely passed over the tracks before the blast. Earlier, officials were investigating whether the device was planted on the train.

The train's slow speed helped lessen the impact, Doyev said. None of the cars overturned, officials said. Russian television broadcast footage of broken windows on the train and twisted metal on the underside of one carriage.

Authorities said the blast blew a hole into the ground below the track.

All traffic on the line was stopped temporarily while the investigation continued. No group claimed responsibility.

Security officials detonated a land mine found about 160 feet from the site of the explosion, Doyev said. Russia's NTV television reported that authorities were trying to defuse another bomb found on the power line above the track. It was not immediately clear whether that was the same explosive device detonated by authorities.

North Ossetia borders Chechnya, where Russian forces have been fighting rebels for much of the last decade.

The ITAR-Tass news agency reported that the first Grozny-Moscow train will depart from the Chechen capital Sunday morning. The direct railway link was broken off in 1999, when the current war between federal troops and insurgents in Chechnya began. Police will be permanently stationed on the trains, ITAR-Tass said.

Fighting persists nearly five years after Russia sent forces to fight rebels in Chechnya for the second time in a decade. Russian forces had withdrawn after a disastrous 1994-1996 war that killed tens of thousands of people and left the region with de facto independence.

Three soldiers were killed and 11 wounded in the latest rebel attacks and mine explosions in Chechnya, an official in the region's Kremlin-backed administration said Saturday.